1. Field of the Invention
The invention is in the field of chitin dispersions useful in the treatment of wounds as dispersions per se and as certain other products such as paper-like structures which result from the coalescence of chitin in said dispersions.
2. Background and Description of the Prior Art
Chitin is a widely distributed polysaccharide occurring as the structural compound in the form of alpha chitin in the exoskeletons of such crustaceans as shrimp, krill, crabs, and lobsters and in the form of beta chitin in the internal pens of squid. Chitin occurs also in the exoskeletons of some insects and in the cell walls of some fungi. Indeed, chitin is second only to cellulose in tonnage of available natural polymers.
The repeating unit of the chitin polymer is 2-N-acetylglucosamine wherein a small fraction of the amino groups are unacetylated.
Chitin and its derivatives, especially deacetylated chitin, so-called chitosan, and derivatives, are finding increasing use as wound healing adjuvants, metal ion scavengers, waste water treatment and food processing compounds, and cosmetic aids.
A major deterrent to the wider use of chitin per se is its intractability. Chitin is modestly soluble in a few uncommon solvents. For example, Capozza in German Pat. No. 2,505,305 reported solubility in hexafluoroisopropanol, hexafluoroacetone, and its sesquihydrate. Austin in U.S. Pat. No. 4,062,921 employed dimethylacetamide or N-methylpyrrolidone containing several percent of lithium chloride to dissolve chitin and Balassa et al applied the classical viscose/xanthate process to chitin, as reported in MlT Sea Grant Report, MIT SG 78-7, p.296.
Dispersions of microcrystalline chitin have been prepared, albeit at the expense of significant hydrolytic degradation of the polymer chain, through pretreatment with hot strong acids, as reported, for example, by Dunn et al in U.S. Pat. Nos. 3,847,897 and 4,034,121, Austin et al in U.S. Pat. No. 4,286,087 and Castle et al in U.S. Pat. No. 4,532,321.Yalpani in "Chitin in Nature and Technology", Plenum Press, New York, N.Y. (1986) teaches dispersions of chitin prepared by extensive high pressure shearing, for example, 3 to 40 passes through a high energy mill at pressures of 4,000 to 15,000 psi (281 to 1055 kg/cm.sup.2).
Sagar et al in British Pat. Nos. 2,182,560 and 2,188,135 teach the preparation of wound dressings, inter alia, by pouring a slurry of washed fungal mycelia into molds or onto a continuous paper-making apparatus, and freeze-drying the resultant mat. The mycelia are bleached before employment in a wet bandage.